Aerating apparatus



June 24, 1941. A. J. WEINIG 2,246,559

AERATING APPARATUS 7 Filed June 22, 1939 4 Sheets-Sheet l 9 INVENTOR.Fig.2. 4/? T'lfl/f? J wsnwe June 24, 1941. W NIG 2,246,559

AERATING APPARATUS Filed June 22, 1939 4 Sheets-Sheet 3 Figs.

INVENTOR. M11101? J WE/lV/G June 24, 1941. J wgm 2,246,559

AERATING APPARATUS Filed June 22, 1959 4 Sheets-Sheet 4 19/1 lune;INVENTOR. A/Pnw/RJ WEI/W6 ATTORN S.

Patented June .24, 1941 UNITED STATES PATENT OFFICE nam'rnfi fiifmarusArthur I. Welnig, Golden, Colo. Applicatlzn (GEE-2:32:0- 280,595

This invention relates toaerating apparatus employed in the treatment ofsolids in liquid suspension and is particularly adapted for use invarious froth flotation treatments in which aeration is an essential. v1 F The present application is a continuation-inpart of my application,Serial No. 119,510, filed I January 7, 1937, for Method of and apparatusfor flotation agitation;

which latter application stands abandoned as of August 7, 1939.

In the well-known froth flotation process, it is essential that thefinely-divided particles of ore or other solid matter are subjected tothe action of certain reagents. Thereafter, by bringing cer talnconstituents of the solids and liquid mixture comprising the pulp intointimate contact with air or other gas dispersed and distributedthroughout the liquid body, certain ofthe constituent solids formattachments to the bubbles of gas and are elevated thereby to thesurface where they collect in a froth. This frothmay be removedseparately from other constituents of the pulp remaining in non-floatedcondition below the froth bed.

While the selection and collection of the floated constituents aredetermined by the re-' agent action, the mechanical action of theprocess, namely, the production of gas bubbles and the contact of thegas with coated solids to promote the elevation thereof, is a functionof the gas distribution which is essential to any such process.-

In such a treatment, the solids in liquid suspension are more or lessuniformly distributed through and held in suspension in the liquid mass,and the efl'lciency of the operation, to a large extent, is determinedby the amount of surface contact between solids and gas produced in theoperation.

Due to the manner in which the materials ar introduced into thetreatment, as well as the nahigh velocityIto induce a mixing of pulp. asand reagent in an agitation zone and thereafter moving the mixedmaterial into a separation zone having a relatively quiescent action inwhich the flotation separation is completed. Generally such machinesemploy alower agitation zone with a separation zone above suitablyseparated by grids, baflles or other suitable devices.

In this way, agitation is restrained so that the effects thereof areconfined largely to the agitation zone and the mineral particlesattached to the gas bubbles in rising'to the froth are more or lessunimpeded in the separation zone.

Despite this general condition, there is sufficient swirl within theliquid body of the separation zone to induce a mingling betweenparticles in suspension and those particles that are being elevated byattachment to the gas rising to the surface. Further, there is in anygiven volume of pulp within the agitation zone a certain percentage ofheavier particles thrown upwardly by the mechanical agitation, which isdescending by gravity to the agitation zone.

face in an ascending action in the same zone or ture of the attachmentsaforesaid, excessive aethe liquid is gentle or at least within velocitylimits which do not produce excessive turbulence.

\ While froth-flotation operations may be performed with a variety ofmachines, present practice shows a decided preference for machines ofthe -mechanical agitation type in most treatments. Such machines employrotary impellers operating within the liquid body at relatively regionin which another portion is descending by gravity. Obviously, under suchconditions the falling particles will destroy the attachment of the gasbubbles contacted within the liquid body and by so doing, release thepreviously attached mineral which thereupon falls untilsuch time as itis again entrapped by contact with rising gas bubbles or is elevated insuspension by the velocity of the agitation.

Recognizing both the beneficial and deleterious effects of suchoperating methods, the present invention has been designed to satisfythe requirements in a treatment in which mechanical agitation isutilized to induce a sufllcient dispersion of gas to satisfy theelevating requirements in a controlled movement in which the disruptionof elevating attachments has largely been eliminated.

It is an object of the present invention to produce a finer distributionor dispersion of gas throughout the body of solids in liquid suspensionthrough the medium of mechanical agitation in an action in which therate of rotation of mechanical agitators has been reduced to decreasethe horsepower requirements of the operation.

vAnother object of the invention is the provi-. sion of a novelapparatus for mixing gas with pulp and/or reagent under the influence ofmechanical agitation to induce a high degree of surface contact betweengas and solids of the pulp while reducing turbulence in the body ofmaterial under treatment subject to the influence of mechanicalagitation.

A further object of the invention is to. combine with the mixing actionof the type described a combined pumping and sweeping action on solid;settling from the treatment for their recirculation through the mixingstages of the operation.

A still further object of the invention is the provision of novelaerating apparatus adapted to control the movement of materials througha zone of agitation in such a way that excessive wear is eliminatedwhile mixing is promoted.

A still further object of the invention is the provision of aeratingapparatus in which the extent and degree of aeration is variable andunder regulation.

Other objects reside in novel combinations and arrangements of parts,all of which will appear more fully in the course of the followingdescription.

Another condition of considerable consequence in the development of thepresent invention, has been the influence of altitude upon the flotationoperation. Frequently, the mills in which the ores are treated arelocated at elevations between 9,000 and 12,000 feet and at such highaltitudes the rarefied air does not afford a satisfactory supply formachines employing the suction action of impellers for entrainment ofatmospheric air as the aerating medium.

The present invention satisfies the requirements of such an operation byemploying gas under pressure (usually compressed air) as the medium foraeration of the pulp. Further, by defining the effective upper and lowerlimits of the gas pressure and providing means for regulating thepressure of the gas delivered to the machine, a highly eflicientoperation is attained which is not influenced by the variable factors ofaltitude and air density.

In order to produce the desired mixing, two streams of material aremoved in parallel and preferably in superposed relation to a point ofdischarge in which the streams are brought together in convergingrelation and immediately thereafter or simultaneously therewith areejected into the more or less static body of the pulp in which theflotation separation occurs.

Preferably, the parallel travel occurs within a rotary impeller in whichprovision is made for suitable division and separation of the twostreams during at least a part of their movement under the centrifugalinfluence of the impeller. To this end, a central opening is providedinto the uppermost chamber into which a mixture of pulp, andrecirculated and partially aerated pulp are brought together.

At the point of pulp introduction into the impeller, a nozzle connectedwith a suitable source of gas supply delivers the gas under pressureinto this uppermost chamber and preferably in a direction correspondingto the movement of pulp through the chamber.

The lowermost chamber draws in pulp not yet subjected to the aeratinginfluences of the flotation cell, which may be supplied either through apulp inlet entering the bottom of the cell beneath the impeller or fromthat portion of the pulp in the cell which is below the impeller andconsequently contains little or no undissolved air.

Such an arrangement results. in the uppermost compartment running in anoverloaded contrance and the presence of large amounts of gas in theliquid body within the compartment at any given moment. The lowercompartment, due to the absence of any substantial quantity of air andbecause the material is drawn in by the pumping action of the impeller,is always in an underloaded condition. The materials of the two streamseven when moving in parallel but passing beyond the physical division ofthe partitioning member of the impeller will be brought into convergingrelation because of a partial vacuum condition developed through theunderloaded condition of the lower compartment which is immediatelysatisfied by the excess pressure on the material in the upper streaminduced by the overloaded condition.

As a consequence of such action, large amounts of air are entrained inthe streams of material at the point of convergence and due to thethorough and intimate intermixture of air, solids and/or reagent withinthe liquid body, the pulp so treated on moving beyond the sphere ofaction or the impeller will assume an elevating movement adjacent thesides of the cell in which the gas in it finely-diffused condition willrise to the surface, carrying with it the minerals attached or attachingthereto during its ascension.

The central opening to the impeller draws in liquid and solids from thezone of the liquid body immediately above the same and because of thedemands of the upper mixing compartment for material, there is apronounced downward movement through the central zone of the cell intothe impeller.

As a result of such forces, the mixing action of the present inventionsets up a .pronounced circulatory movement in which solids not entrappedin the air bubbles, .but elevated by the agitating action, are drawninto the central portion of the cell before they assume a gravitationaldescent, while the mineralized particles which have formed attachmentswith the gas rise without impedance through the ascending column of thecirculatory movement.

From the foregoing, it will be apparent that the present invention maybe applied generally to machines of the mechanical agitation type andwhen so applied, is productive of a distinctive type of operatingprocedure that attains highly beneficial results.

While many structural arrangements may be employed to perform theoperations of the present process, certain structural embodiments haveproved highly effective in attaining the desired objects.

In order to afford a better understanding of the invention, referencewill now be made to the accompanying drawings, in the several views ofwhich like parts have been designated similarly and in which: a

Figure l is a side elevation of a typical flotation cell of thesub-aeration type to which the present invention has been applied;

Figure 2 is an enlarged sectional view of the impeller constructionillustrated in Figure 1;

Figure 3 is a side elevation of another typical sub-aeration cell towhich a modified form of the invention has been applied;

dition due to the hydrostatic head above the en- Figure 4 is an enlargedsectional view of the impeller construction illustrated in Figure 3;

Figure 5 is an enlarged sectional view of a modified type of impellerconstruction;

Figure 6 is a side elevation of another subaeration cell with anothermodification of the imor other receptacle (not illustrated).

The tailings discharge of the cell comprises an outlet l6 controlled bya float-actuated valve 11 determining the liquid level in the cell. Arotary shaft l8 driven in any suitable manner extends from a point abovethe tank 8 into the lower portion of the same and carries at its lowerend a rotary impeller l9.

Gas under pressure is carried in a header 20 supported on the tank andconnected with one or more conduits 2| which extend downwardly into thecell and terminate in nozzles 22 discharging through a central opening19a into the upper portion of the impeller i9. Control of gas dischargeis provided through the medium of valves 23.

In certain treatments, it will be desirable to introduce reagentsdirectly into the cell and utilize the agitation and aeration of thetreatment as a means of attaining the proper mixing of re-- Usually,such reagents v'll be of the water soluble type, such as xanthates,

agent and solids.

cresylic acid and pine oil, and are often so introduced in the treatmentof copper, lead and zinc ores.

To this end, a reagent feeder is incorporated in the cell structure andcomprises a funnel 24 at the upper end of a conduit 25 extending intothe opening I9a of the impeller and discharging adjacent one of the gasdischarge nozzles 22.

The form of the impeller illustrated in Figures 1 and 2 has top andbottom plates lab and I90 respectively, separated by a dividing memberor partition l9d carried on a hub member He mounted on the shaft 18 toform superposed chambers A and B. In this form of impeller the bottomplate 190 has a central opening lBg to admit matter from inlet l4 intochamber B.

The dividing member [9d of this form of impeller is of a diameter equalto that of the top and bottom plates i9b and He and the chambers A and Bhave separate peripheral openings for the discharge of material into amixing zone exterlorly of the impeller. Vanes, I971, preferably inradial arrangement, extend to the periphery from a point adjacent thecenter of the impeller and connect the top and bottom plates with thedividing member.

By the action of the vanes in compartments A and B, the two currents areforcibly ejected beyond the periphery of the agitator, with the currentejected from compartment B taking an outward trend, while the streamdischarged from compartment A takes a downward trajectory ow- I ing tothe partial vacuumcreated in the lower compartment B as previouslyexplained.

The provision for impinging the streams beyond the periphery of theimpeller and delivering relatively large quantities of air into the pulpbody bordering the impeller, causes a 1*gh degree of intermingling ofthe ejected mi are with the pulp bodyin the cell and the action furtherserves to diminish frictional resistance to such an extent that thimpellers may be operated at a speed of approximately one-third lessthan the requirements of present practice without impairing the qualityof aeration and, in fact, improving the same.

In order to preserve the horepower reduction thus attained, the airshould be introduced as near the center of the impeller as possible anddue to the balance required in the impeller when operating at highspeeds, the inlet opening must be concentric with the shaft. Such anarrangement permits reduction in the size of the impelling vanes forejection of the matter delivered to the chambers A and B for the size ofthe vanes must be increased proportionately to the distance from thecenter at which the material is introduced.

Theoretically, the upper-compartment should be narrower than the lower,but obstructions such as wood chips, etc., entering with the feed makeit impractical to so reduce the passage in the standard sizes. However,in larger sizes such an arrangement would be preferable.

On the other hand, if the lower chamber is narrower, much of theaerating efiect is destroyed with increased turbulence and boiling inthe cell which lowers recovery.

The arrangement of the air pipes and reagent feed of Figure 1 is alsoadvantageous in the operation. The air pipesare so designed that acleaning rod may be inserted through the top at the normally-closedopening 26 and from such position will penetrate through the dischargenozzle 22 when the opening i in the angular position indicated in Figure2. This feature is of particular value in starting the machine followingshut-downs and the like, which sometimes occur, causing the solids tosettle out of suspension and fill the lower portion of the flotationcell.

The location of the pipes 2| and 25 with reference to the inlet opening19a serves to prevent any vortex action in the material entering theinlet by restraining the swirl above the same at the same time that thedischarging gas fills the void, which otherwise would be present belowthe opening.

Hlving thus described the structural arrangement, reference will now bemade to the operating procedure within the cell. Pulp from. a suitablesource of supply, such as a classifier, conditioner or preceding cell ina series enters through inlet it into the agitating compartment I! whiletailings of the treatment discharge from the cell through outlet it at arate determined by the float-actuated valve mechanism II.

This discharge control determines the liquid level in the cell, whichusually is maintained in close proximity to the elevation of overflowl5. On entering chamber l2, the pulp it drawn into compartment B ofimpeller l9 by its suction influence, and upon being subjected to thecentrifugal influence and the action of the vanes Hi is moved in alengthwise direction through the compartment and discharge into the pulpbody in the cell. At the same time, a portion of the previously aeratedpulp recirculates through opening Ha into the upper compartment A of theimpeller and there impinges upon the streams of air discharged throughnozzles 22 and by the action of the vanes l9h and the centrifugalinfluence, moves in substantially parallel relation to the pulp streamin chamber B.

- The underloaded condition of compartmentB creates a condition ofpartial vacuum which at the peripheral termination of dividing member IMpermits the overloaded condition of compartment A to satisfy therequirement of the material passing out of chamber B. As a result, thereis a pronounced downward trajectory of the material discharging fromchamber A into impinging relation with the discharge from chamber B.This impingement causes the high degree of intermixture and gasdispersion previously described.

In cells in which pulp enters through a bottom opening and i thensubjected to the pumping action of the impeller, it is preferredpractice to locate the impeller in close proximity to the inlet openingto prevent dissipation or losses of the suction influence.

Due to the shape of the cell and the movement of the discharging liquidunder the influence of the impeller, coupled with the buoyant conditionof the mass, the solids in suspension and the mineral entrapped by theair in the flotation action are caused to rise in a column movingsubstantially parallel with the upright walls of the cell. A theascension progresses, that portion of the solids content which is notbeing elevated by the flotation reaction is drawn toward the center ofthe cell and when the gravitational eiIect overcomes the suspensiontendencies on such particles, they descend in the central zone of thecell to return for further treatment through the inlet opening Isa.

In this manner, a pronounced and well-defined circulatory movement isset up in the cell, as indicated by the directional arrows in Figure l,in which the elevated and descending columns of material are definitelyeparated, eliminating impedance of the elevated material of theflotation reaction and puncturing of the mineralladen bubbles, as wouldotherwise occur.

Whenever it is necessary to introduce reagent to a given cell, suchreagent may be placed in funnel 24 and delivered through conduit 25 intothe mixing zone of chamber A. Due to the proximity of the point ofintroduction of the reagent to the gas discharge into such chamber, thegas will assist in carrying the reagent into solution and the mixingaction will be effective in bringing such solution into repeated andintimate contact with solids passing through the mixing zone.

The form of the cell to which the invention has been applied asillustsated in Figure 3, is one in which the feed to the machine eitherfrom an outside source or a preceding cell, enters the cell at anelevation above its bottom.

In order to provide a feed for compartment B of impeller ii) of thisform, which is substantially free of gas, the impeller is spaced at adistance from the cell bottom to insure a portion of the liquid bodyacted on by the suction influence of the impeller being free of gaspreviously ejected through the peripheral openings of the impeller.

In this form, gas is introduced into compartment A through conduits 22in the manner previously described, and recirculating pulp which hasbeen at least partially aerated by the previous action of the impeller,returns through the opening i 90. and mixes with the gas before itsejection from chamber A. The impeller exerts a pumping action at thecentral opening lag to draw settled solids along the bottom and toelevate solids and liquid into the chamber B.

As a consequence, the material under treatment in this form of cell issubstantially identical with that previously described and except in therespects noted, the operation performed in the cell of Figure 3 isidentical with that performed in the cell of Figure 1.

The form of impeller illustrated in Figure 5 employs the same mixingprinciple as the impeller of Figure 2, for example, but the dividingmember lid in this form of construction terminates at a substantialdistance from the periphery of the impeller.

Again, in this form, the chamber A is operated in an overloadedcondition, while the chamber B is operated in an underloaded condition,

Due to the pressure differential between the materials of the respectivechambers, the stream of pulp ejecting from the passage defined inchamber A assumes a downward trajectory and impinges on the materialtravelling through chamber B, adjoining but inside the periphery of theimpeller. As a consequence, a substantial portion of the material thrownout by the impeller is premixed and thoroughly aerated before itentersthe substantially static body of pulp beyond the impeller.

As in the other forms of impeller previously described, pulp is drawn inthrough the central bottom opening of chamber B and the vanes |9h assistin the impelling movement of the pulp through the chambers. Sweepingblades lam are shown on the bottom of the'impeller and move settledsolids on the tank bottom back into suspension in the liquid body.

In Figures 6 and 7, a form of construction is illustrated in which theimpeller housing is of conical form. As clearly illustrated in Figure 7,the impeller contains the usual dividing member it which terminatesshort of the periphery of the impeller to .provide a mixing zoneadjoining but within the periphery of the impeller.

While the impeller illustrated has a sharp inclination to its conicalsurface, it will be obvious to those skilled in the art that any desireddegree of inclination may be used, and if desired, the conical coverportion need not extend in encompasslng relation to the dividing memberin constructions in which only a slight pitch is employed.

In such an impeller, the vanes in the chamber B are an essential,particularly if the bottom plate is omitted, as illustrated. Theprovision of the vanes lBh in this form of construction insures adequatepumping action to draw substantial quantities of pulp into and throughchamber B and as in the other types of impellers, the second stream ofpulp, moving through compartment A assumes a downward trajectory,induced in part by the pressure differential of the streams and also bythe crowding action of the inclined surface to impinge upon and mix withthe pulp stream of compartment B as in the other forms of the invention.

The construction of Figure 7 necessitates a convergence of the streamswithin the impeller enclosure and the ejection of the mixture at thelower edge of the cone.

The foregoing description illustrates a condition of general applicationto all the forms illustrated herein, namely, that under favorableconditions the bottom plate may be omitted without destroying thefunction and identity of the chamber B and the pulp in which theimpeller is immersed will enter centrally of the lower compartment andbe discharged at its periphery by the action of the pumping vanes.

Thus, it is apparent that th mixing function of the present constructionmay be embodied in a variety of forms to satisfy difierent operating andmanufacturing requirements and in all such forms the horsepower savingspreviously described will be effected and a highly eflicient mixingaction will be attained.

Further, with respect to the flexibility of the 4 present construction,it will be noted that the dividing member defining the compartments Aand B may be of a lesser diameter or the same diameter as the upper orlower plates of the impeller. Also, the length of the impelling vaneswithin the impeller may be varied and while a shortened vane ispreferable from the standpoint of horsepower requirements, under somecircumstances as when the bottom plate is omitted,

it may be preferable to have longer vanes in the lower compartment atleast.

The impellers may be composed of separate parts suitably fastenedtogether or may be inito discharge gas into the pulp stream enteringtherethrough in the direction of its movement.

2. In aerating apparatus, a rotary hollow body having in its top anopening around its axis of rotation for admission of pulp, a dividingmemher in the body defining upper and lower chambers therein, therebeing an inlet opening in the body for admission of pulp to the lowerchamber, vanes in both chambers for impellent action on the pulpadmitted through the respective openings, and means for introducing gasunder pressure into the pulp as it enters the impeller through the upperopening.

tially formed as an integral unit and the simplicity of the presentdesign makes possible the adaptation of the impeller in a variety ofma-.

that changes in any one form may be incorporated in accordance with thedisclosures of the other forms.

i'he setting of the lmpeller'in the tank likewise is subject tovariation. Where the feed enters the cell from underneath, it ispreferable to have the impeller operating in close proximity to the feedinlet to exert the strongest possible suction influence thereon, butwhere conditions require, the spacing of the impeller from the inlet maybe varied if necessary.

Similarly, in machines in which the feed enters the tank other thanthrough a bottom opening, it is preferable to have the impelleroperating at a distance from the bottom in order to provide a portion ofthe pulp body adjacent the bottom which is substantially free from gas.However, any means of providing a liquid body free from gas other thanthe s acing of the impeller, will satisfy the needs of the presentinvention and is with n contemplation thereof.

The introduction of the reagent has only been shown in connect on withthe impeller form of Figures 1 and 2, but it will be understood that thefunnel 24 and associated conduit 25 may be incorporated in all of theembodiments of t e invention where reagent feed direct to the cell isan. essential operating requirement.

What I claim and desire to secure by Letters Patent is: r

1. Apparatus of the charact r de cribed, comprising a tank for solids inliquid su pensi n.

open to the atmosphere, a rotary im e ler in the lower portion of thetank divided into u per and the delivery of gas from the source into theimpeller and provided with a nozzle extending 3. In aerating apparatus,a rotary conical body having in its top an opening around its axis ofrotation for admission of pulp, a dividing member in the body definingupper and lower chambers therein, there being an inlet opening in thebody for admission of pulp to the lower chamber, vanes in both chambersfor impellent action on the pulp admitted through the respectiveopenings, and means for introducing gas under pressure into pulpentering through the upper opening.

4. Froth flotation apparatus, comprising a tank having a feed inlet anda discharge outlet determining a liquid level therein and divided into alower agitation compartment and an upper separation compartment, arotary impeller in the lower portion of the agitation compartment at adistance from the bottom thereof and comprising upper and lowerchambers, separately open adjacent the periphery of the element for theseparate discharge of two currents of pulp into a mixing zone adjoiningsaid periphery, both chambers having openings to admit pulp centrallythereof, and conduit means extending from above the liquid level andterminating at the central opening in the upper chamber of the impellerfor the delivery of gas under pressure thereto.

5. Froth flotation apparatus, comprising a tank having a bottom feedinlet and a discharge outlet determining a liquid level therein anddivided into a lower agitation compartment and an upper separationcompartment, a rotary impeller in the lower portion of the agitationcompartment in close proximity to the bottom thereof, and comprisingupper and lower chambers, separately open adjacent the periphery of theelement for the separate discharge of two currents of pulp into a mixingzone adjoining said periphery, both chambers having central openings toadmit pulp thereto, conduit means extending from above the liquid leveland terminating at the upper central opening for introducing gas underpressure into'pulp entering therethrough, and vanes in the lower chamberto accelerate outward movement of vpulp through the peripheral openingthereof.

6. In flotation apparatus, a.' cell open to the atmosphere having a feedinlet and a discharge outlet determining a liquid level therein, arotary impeller within the body of pulp having upper through the uppercentral opening in a position and lower chambers and having a centralintake opening in each of said chambers, and mean; for

introducing gas above atmospheric pressure into the uppermost of saidintake openings to induce with the hydrostatic pressure of the pulp, anoverloaded condition in the upper chamber while the -lower'chamber ismaintained in an underloaded condition by the absence of gas at itsintake opening.

- ARTHUR J. wanna.

